DUNEDIN, Fla. (AP) - Residents of several Florida homes have been evacuated due to a possible sinkhole that opened in a backyard in Pinellas County on Thursday.

Dunedin Deputy Fire Chief Trip Barrs said the hole appeared to be about 12 feet wide when officials arrived on the scene. Residents of the neighboring houses also were evacuated as a precaution.

The Tampa Bay Times reported that the ground was so unstable, two homes had to be demolished.

Television footage showed part of a patio caved in and a boat on the edge of the hole. Tampa area television stations reported that a neighboring pool appears to have cracks.

The affected neighborhood is in Dunedin, a small city in northern Pinellas County, about 20 miles north of St. Petersburg.

Sinkholes are common in Florida because the peninsula is made up of porous carbonate rocks such as limestone that store and help move water underground. Over time, the rocks can dissolve from an acid created from oxygen in water, causing a void under the limestone roof. When dirt, clay or sand gets too heavy for the limestone roof, it can collapse, creating a sinkhole.

On Feb. 28, Jeffrey Bush died when a sinkhole opened under his bedroom in Seffner, Fla., near Tampa. His body was never recovered. In August, sections of a building at a resort near Orlando collapsed into a sinkhole. No one was injured.

Homeowner Michael Dupre said the family heard a noise that sounded like a sledgehammer pounding on the wall early Thursday morning.

Dupre told Bay News 9 there had been "sinkhole activity" in the area. "After the Seffner sinkhole, we were scared. We've been dealing with our insurance company and finally two days ago, they started working on our house. Now it looks like our house is gone."

As the hole grew, it swallowed the Dupres porch and new boat. Now, his neighbor's swimming pool and a portion of that home have fallen in as well.